Conventional cellular phone systems have enjoyed considerable popularity and growth in recent years. The basic structure of cellular or mobile phone systems presently implemented use a network topology generally referred to as a "star" system. This term arises from the network characteristic in which the plurality of mobile cellular phone units allows all calls to other mobile units or conventional wired phone network units through a central or base facility. In present cellular system technology, a plurality of such base units or cell sites are arranged to provide service to mobile units within their local areas. Thus, for example, a mobile unit is able to communicate with the cell site or base unit within its closest proximity or strongest signal condition as the initial step in establishing communication with other mobile units or through conventional wired phone system networks to virtually any conventional telephone user. While the use of plural cell sites as opposed to a single central facility has greatly enhanced the practicality of cellular mobile phone operation, present day mobile phone systems remain susceptible to poor quality or call interruption or blockage due to various electromagnetic obstacles encountered. In the event an electromagnetic obstacle such as a geographic feature, a substantial building, or other interfering structure is interposed between a mobile unit and the cell site or base unit, service to and from that mobile is rendered impossible. The present cellular phone systems attempt where possible to compensate for such barriers by positioning the plurality of base sites to maximize coverage of a given area of interest.
The vast majority of cellular mobile phone systems in operation utilize analog technology which further limits the effectiveness and reliability of network communication due to the greater susceptibility of interference and greater signal strength required for communication. In addition, conventional cellular phone systems operate using a pair of control channels and a pair of data channels to set up and enable calls between a mobile unit and the central base facility or cell site. The central unit transmits on the forward control channel while the mobile unit responds on the reverse control channel. The central unit or cell site then assigns a pair of data voice channels one for each direction of cellular phone communication. Because these data voice channels utilize different frequencies for transmission, additional problems are created which are particularly acute in weak signal areas. The frequency difference in data/voice channels for each direction results in different transmission characteristics with respect to geographical problems and obstacles. As a result, one unit, either central or mobile, may have clear transmission or reception while the other has weakened or noisy transmission and reception.
Recognizing the limitations of present analog cellular phone systems, practitioners in the art have been attempting to overcome these limitations utilizing various digital communications systems. While a substantial number of such digital communication systems have been suggested, particular promise is shown in systems such as Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). Both TDMA and CDMA are the subject of substantial interest within the United States of America. Within Europe and many other areas, a form of TDMA known as Global System Mobile (GSM) is the subject of substantial interest. The operating parameters and formatting of such digital systems varies substantially. However, all generally attempt to utilize the improved capabilities and flexibilities of digital communication systems in overcoming the limitations of present analog cellular mobile communication.
U.S. patent application (abandoned), which is also the subject of an international publication WO95/11561 filed by Michael R. Lynch and Richard L. Tamplin sets forth a TRANSCEIVER WITH CALL SWITCHING CAPABILITIES IN ARBITRARY NETWORKS having a novel feature which utilizes relay capability between mobile units to extend the network communication coverage. This system substantially improves network topology in that the reliance upon communication directly between each mobile unit and the base or cell site is not necessary for call routing. In the system shown, an originating station or unit is able to communicate with a remote or obstacle impaired unit through one or more relay stations or units. The selection of call routing path is selected so as to minimize transmission power in the event of multiple or alternate paths being available. Despite the improvement provided in the above-described prior art system, there remains a continuing need in the art for evermore improved effective and efficient distributed wireless call processing systems.